1. Along‐Strike and Downdip Segmentation of the Pamir Frontal Thrust and Its Association With the 1985 Mw 6.9 Wuqia Earthquake.
- Author
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Li, Tao, Chen, Zhuxin, Chen, Jie, Thompson Jobe, Jessica A., Burbank, Douglas W., Li, Zhigang, He, Xiaohui, Zheng, Wenjun, Zhang, Peizhen, and Zhang, Boxuan
- Subjects
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EARTHQUAKE hazard analysis , *THRUST faults (Geology) , *SEISMIC reflection method , *CENOZOIC Era - Abstract
The Pamir Frontal Thrust along the leading edge of the northern Pamir is characterized by multiple earthquakes with moment magnitudes of 6.5–7.1. Geometric characteristics of the Pamir Frontal Thrust corresponding to these earthquakes and to future seismic hazards, however, remain largely unexplored. This study focuses on the easternmost segment of the Pamir Frontal Thrust, where the Mw 6.9 Wuqia earthquake occurred in 1985. Through interpretation of available two‐dimensional seismic reflection profiles and surface mapping data, we develop a three‐dimensional geometric model for the fault plane. Our results illustrate that, at depth, the fault plane is separated by a subhorizontal detachment horizon into upper and lower ramps, and both ramps are significantly segmented, along strike, by transfer faults or lateral ramps as well. Such along‐strike and downdip segmentation of the thrust sheet apparently plays a significant control on seismic rupture process of the Wuqia earthquake and can well explain why the region is characterized by moderate‐magnitude (Mw 6.5–7.1) events. Additionally, our study helps quantify key constraints on the Cenozoic deformation and evolution of the northeastern Pamir and, specifically, determines a total shortening of ≤43 km at the Pamir front: accommodating about 15% of the total indentation of the Pamir range into central Asia. Key Points: The PFT fault plane is significantly segmented both in the downdip direction and along strikeRupture of the 1985 Wuqia earthquake is likely encompassed within the upper ramp of the Tuomuluoan PFT fault segmentTotal shortening at the Pamir front is ≤43 km: significantly less than ~300‐km‐northward Cenozoic indentation of the Pamir [ABSTRACT FROM AUTHOR]
- Published
- 2019
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